In the last sequence I took around Christmas 2008 with my old Canon EOS 400D (XTi), I realised that there was lots of dust spots in the images. Unfortunately, the HDR processing amplifies these dark spots even more. Luckily, the spots stayed for the whole series at the same position.
To remove the dust, Photoshop has a nice filter (filter... noise filters... dust and scratches). However, if this is applied to the whole image, it will become fuzzy. To prevent this, I followed these steps:
- Use Layer... dublicate layer.
- On the dublicated layer select all dust spots with an Elliptical Marquee (tools). If there are several spots, use the SHIFT key to select all spots.
- In the layer window use Add Layer Mask...
- In the Layer window: Click onto the small image in the background copy to unselect the layer mask. Then use the filter in: filter... noise filter... dust and scratches filter... Leave the threshold at 0, and change the radius until the dust is gone. Values around 20-60 are usually fine.
To batch process the dust removal, you can define an action. Do not forget to save and close the image at the end. I then use Adobe Bridge, mark the images I want to batch process, go to Tools... Photoshop... Batch to run the action defined before, and change the target to the path I want to save my images.
Here you can download the action. To customize, you have to change the settings of the filter and the selection of the dust spots.